Effects of work surface height on muscle activity and posture of the upper extremity during simulated pipetting

Abstract

In order to examine the effects of work surface height (WSH) on muscle activity, posture and discomfort during simulated pipetting, an experimental study was conducted using electromyography, electrogoniometry, video techniques and also qualitative data. The experimental design consisted of one independent variable (WSH with six heights) and 13 dependent variables. The levels of muscle strain and discomfort were significantly lower at the shoulder when the WSHs were low but thumb muscle activities and neck flexion levels were markedly higher at these WSHs compared to higher WSHs. To reduce shoulder strain, without raising thumb and neck strain beyond acceptable limits, the findings suggest that the height of a laboratory workbench should be at the level of the pipette tip when held in a standing position with the hand at elbow height. It was also found that pipetting should not be done in a seated posture.

Practitioner Summary: An experimental study was conducted to examine the effects of work surface height on upper extremity muscle activity, posture and discomfort during simulated pipetting. The findings suggest that the laboratory workbench height should be at the pipette-tip level when held in a standing position with the hand at elbow height.

Keywords:

• work surface height
• muscle activity
• posture
• discomfort
• pipetting

Acknowledgements

The authors wish to acknowledge volunteers at the UML and also thank Drs Narendra Vaidya and Bong-Kyoo Choi, and Shardul Patel for input on experimental set-up, and Drs Laura Punnett, Susan Woskie and Rebecca Gore for review of an early version of this paper. This investigation was made possible by Grant No. T42 OH 008416 from the US National Institute for Occupational Safety and Health (NIOSH). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIOSH. Earlier versions of this study were presented at different conferences and meetings.